The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of a knock control system 100 according to the prior art is presented. The knock control system 100 includes an engine 102, which includes multiple cylinders 104. The engine 102 includes a vibration sensor 106 that measures vibration of the engine 102. Vibration may be caused by early detonation within the cylinders 104, also referred to as knock. In various implementations, the vibration sensor 106 may include a piezoelectric accelerometer.
An output of the vibration sensor 106 is received by an analog to digital (A/D) converter 110. The A/D converter 110 digitizes the output of the vibration sensor 106 and communicates the digitized output to a digital signal processor (DSP) 114. The DSP 114 performs a Fast Fourier Transform (FFT) on the digitized output. The frequency content of the digitized output is transmitted to a knock detection module 116.
The knock detection module 116 determines whether knock is occurring based upon the frequency content of the output of the vibration sensor 106. The knock detection module 116 may select a peak intensity or an average intensity across the frequencies of the FFT calculated by the DSP 114. The knock detection module 116 may compare the average or peak intensity to a threshold intensity and determine that knock is present when the threshold intensity is exceeded.
The knock detection module 116 may adapt the threshold intensity to background vibration unrelated to knock that is present in the engine 102. The knock detection module 116 transmits knock information to a knock control module 118. Based on the knock information, the knock control module 118 varies operating parameters of the engine 102 to reduce knock. For example, the knock control module 118 may instruct the engine 102 to retard spark.